If your talking about editor what I find best to do when I press something I should not have pressed is this.
When you get editor up look at top left you will see modes then a down arrow then a P.
Click on down arrow and select show then restore to default and see if that works.

Haha, its just throwing the editor back into a default state, the game will generate all new fresh ones when you re-launch it.. it's the same deal when you remove/change config files for the game or the game updates and you have to redo your keybinds..

Kinda does sound like a global lighting issue though.. did you overdo the brightness of your dominant directional light, and/or playtesting in editor without building the lighting first?

If things are really bad and nothing you do seems to fix it, you can always remove the various editor ini config files from the Documents location, I've found that can sort out an issue or two

Close Editor.. then go to and remove highlighted above, reload editor and hope its all better

So I did this, opened the map back up and the whole thing was white lol.. I switched to wire mode Deleted the Main light source and it was back to normal.. tried play from here and it worked too soo ya.. lighting issue for some reason.